Zinc lozenges and tablets or sprays can be an effective prophylactic and treatment for mild-to-moderate respiratory tract infections, Australian researchers have found.
Although the immunological mechanism remains unclear, findings from their meta-analysis provide further backing for expanding the role of the nutrient, they say.
Zinc also provides GPs with an alternative management option when dealing with patients who ask for an inappropriate antibiotic script, the Western Sydney University-led team suggested.
When used for prevention, zinc use was associated with a 32% and 28% lower risk of developing mild-to-moderate symptoms consistent with a flu-like illness or the common cold, respectively.
In contrast, no significant benefits were seen for prophylactic zinc among patients in six trials who were purposely infected with human rhinovirus, the authors said.
Looking at treatment, zinc reduced symptom duration by two days and participants who used sublingual or topical nasal formulations in the first week of illness were 1.8 times more likely to recover before those given placebo.
Zinc was also associated with a clinically important reduction in day three, but not daily average, symptom severity scores, the study found.
And while there was an increased risk of non-serious adverse events, such as nausea, mouth irritation or soreness — which the authors say “may limit tolerability for some” — the risk of serious reactions was low.
“The marginal benefits, strain specificity, drug resistance and potential risks of other over-the-counter and prescription medications makes zinc a viable ‘natural’ alternative for the self-management of non-specific RTIs,” they wrote in BMJ Open.
The daily dose of oral zinc used as a prophylactic was 15mg or 45mg for seven or 12 months, respectively.
Sublingual lozenges to treat or prevent community inquired infections had doses of between 45mg and 300mg per day and were used for up to a fortnight, whereas nasal sprays used for prevention or treatment used lower doses at 0.9mg to 2.6mg per day.